The present invention relates to a method of balancing loads on a plurality of packet processing apparatus and to a packet processing apparatus, and more particularly to a load balancing method and a packet processing apparatus capable of improving a network reliability.
There is a conventional method of switching packet processing apparatus such as switching processing apparatus when any packet processing apparatus fails, without requesting terminals connected to the network to have a new function. For example, VRRP (Virtual Router Redundancy Protocol) is known as a hot standby protocol using virtual IP addresses. For the explanation of VRRP, refer to a document “[Internet-Draft]” Virtual Router Redundancy Protocol, by S. Knight et. al., published by IETF” (see www.ietf.org/internet-draft-vrrp-spec-v2-05.txt).
The hot standby protocol will be described below.
It is assumed that apparatus A and B having a packet relay function are connected to a network and that the apparatus A operates as a working apparatus and the apparatus B operates as a standby apparatus (a reserved apparatus). In this case, the standby apparatus B is in a hot standby state. Virtual link addresses and virtual IP addresses are set to the apparatus A and B. The virtual address is used as a destination address when each terminal connected to the network transmits a packet to the network. A packet having the virtual address as the destination address is generally received by the working apparatus A which in turn relays the packet.
The apparatus A and B monitor each other by periodically transmitting and receiving a packet. If a packet is not transmitted from the apparatus A during a predetermined period, the apparatus B judges that any failure occurred at the apparatus A, and succeeds the packet relay process executed by that time by the apparatus A. At this time, the same virtual link address and virtual IP address are set to the apparatus A and B so that the terminal can continue communications without being conscious of the succession of the packet relay process by the apparatus B.
According to the hot standby protocol described above, the apparatus (apparatus A in this example) for executing a packet relay process and the apparatus (apparatus B in this example) for succeeding the packet relay process upon occurrence of a failure are generally fixed.